life jacket vs life vest

life jacket and life vest both are nouns.

Word	Noun	Adjective	Verb	Adverb
life jacket	Yes	No	No	No
life vest	Yes	No	No	No

As nouns, life jacket and life vest are synonyms defined as:

life jacket and life vest: life preserver consisting of a sleeveless jacket of buoyant or inflatable design

Other synonyms of life jacket include cork jacket.

life jacket (noun)	life vest (noun)
life preserver consisting of a sleeveless jacket of buoyant or inflatable design	life preserver consisting of a sleeveless jacket of buoyant or inflatable design